The present invention relates to a process and apparatus for cooling of partial oxidation crude gas.
A process for cooling of partial oxidation crude gas is known comprising gasifying, i.e. partially oxidizing, a fine grained to powdery combustible material in a flue flow gasifier in the presence of oxygen and/or air and water vapor at pressures of up to 100 bar and temperatures above the cinder melting point to form a crude gas and quenching the crude gas with a gaseous and/or vaporous cooling fluid.
The gasification temperature is from about 1500.degree. C. to about 2000.degree. C. in the gasifying of fine grained to powdery combustible material under the above-described conditions. During the flow of the partial oxidation crude gas flow through the so-called crude gas duct, it is cooled by chemical reactions and by heat transfer to the cooled walls of the crude gas duct. The term "crude gas duct" usually means that section comprising the reactor shaft of the gasification reactor above the burner plane and the pipe section immediately following it which is usually a radiative cooling means. Downstream of the crude gas duct the temperatures of the partial oxidation crude gas are between about 800.degree. and 1600.degree. C. according to the structural height and cooling of the crude gas duct. For additional cooling the gas in the crude gas duct is conducted into a convection cooler or a combination radiation-convection heat exchanger unit. The partial oxidation crude gas produced in the gasifier contains however components, which are deposited from the crude gas flow because of the decreasing gas temperature and which can form deposits both on the walls of the crude gas duct and also in a downstream cooling device. The deposits consist of adhering and/or melted ash and/or cinders. The gas flow and the heat transfer from it are reduced, or even completely stopped or prevented, because of these deposits, which are only removed with great difficulty by currently available means. It is therefore necessary to cool the crude gas downstream of the gasification reactor to such an extent that no deposits form on the walls immediately downstream of the gasification reactor. For this purpose it is already known to mix the hot crude gas stream in the vicinity of the crude gas duct upper of the gasification reactor with a a gaseous or vaporous cooling fluid at a comparatively lower temperature. The method, which is known to one skilled in the art as quenching, can be performed with a cooled product gas feedback, with water vapor and with any other gas which does not adversely effect the desired gas composition. For this purpose various methods have already been suggested in which an input of cooling fluid is provided in a partial flow through a circular gap or a number of entrance openings in the jacket of the crude gas duct, whereby the quenching gas feed occurs either horizontally into or synchronously with the upwardly flowing crude gas. It has been proven that the formation of deposits cannot be avoided under unfavorable conditions. Under unfavorable conditions the deposits can grow until near the quenching region of the crude gas duct and partially block the admission of quenching gas in the crude gas duct, so that the operation of the quenching process is considerably disturbed. Individual cinder pieces can be loosened during sudden pressure fluctuations and then reach the quenching gas guide duct and lodge there. This danger is particularly present with a horizontal quenching gas feed. These deposits are removed only with great difficulty with the standard mechanical cleaning devices because of the plastic surfaces which these deposits have on their hot side facing the crude gas stream.
Another method, in which a portion of the cooling fluid is conducted radially through the jacket of the crude gas duct into the crude gas stream, while the other portion of the cooling fluid is fed by an axial quenching pipe located in the crude gas duct in an opposite direction to the crude gas flow, is described in German Published Patent Application DE OS 38 08 729. This process always presupposes the presence of a suitably arranged quenching pipe. This sort of disadvantage however presents problems from the standpoint of flow engineering.